Cal Spa not shutting down

I just changed the water in my Cal Spa hot tub. It was working fine before. Now it won't shut off even if I set the temperature way low from where it is. It also seemed to take a long time to get up to temperature. I set it for 89 degrees, still running at 91. I set the temp to 80 degrees, still kept running. Any thoughts? Your help is most appreciated.

Does your spa have a digital temperature display? If so does the temperature on the display match what the actual water temperature is using a thermometer? If the display temperature is lower than what the actual water temp is you may have a bad temperature sensor. Have you tried shutting the power off to the spa and restarting it?